1. little man syndrome
"Napolean complex" is already a term. The "little man syndrome" is less literate; unneccessary.
2. Little man syndrome
Condition whereby undersized men compensate for their smallness by physically asserting their presence.
That Puerto Rican just freaked on me when I stepped on his puma—he’s got a bad case of little man syndrome.
Courtesy of http://www.urbandictionary.com/
I'm not sure I totally agree though, I don't think that men need to be short to have LMS. I have known short men who are perfectly ajdusted, I have also know very tall men who have a chip on their shoulder larger than most boulders.